1. Field of the Invention
The present invention relates generally to mobile communication systems, and more particularly to a mobile communication system for dealing with connectionless packets.
2. Description of the Related Art
Mobile data terminals are increasingly used in cellular communication systems to provide TCP/IP (Transmission Control Protocol/Internet Protocol)-based connectionless mode communication via the Internet. Since the cellular communication system is a connection-oriented network, network resource is not utilized efficiently for connectionless mode communications. Furthermore, since the prior art location management is performed by the use of a home location register centrally co-located with a mobile switching center, the delay involved with locating a destination mobile data terminal is significantly large if the data terminal is moving at high speeds. Additionally, it is desirable to perform fast handover operation.
It is therefore an object of the present invention to provide a mobile communication system and method that is suitable for connectionless data communication.
According to a first aspect of the present invention, there is provided a mobile communication system comprising a gateway connected to a connectionless data network, a plurality of routers connected to the gateway, and a plurality of wireless access networks, connected respectively to the routers, for establishing wireless links with mobile stations. The gateway is arranged to transmit a request message to all of the routers in response to a packet from the connectionless data network for requesting a search for a mobile station specified by the packet. Each of the routers includes a memory for storing location data of mobile stations, and makes a search through the memory in response to the request message to receive that packet from the gateway if the specified mobile station is found in the memory, and routes the received packet via the corresponding wireless access network to the mobile station.
The gateway may be arranged to receive a series of packets of same destination from the connectionless data network, and transmits the request message to all of the routers in response to the packet of first arrival for requesting a search for a mobile station specified by the packet of first arrival. Each of the routers is arranged to respond to the request message with a reply message if the specified mobile station is found in the memory of the router. The gateway sequentially transmits the received packets to the router from which the reply message is received.
The gateway may be further arranged to receive a series of packets of same destination from the connectionless data network, transmit a request message to all of the routers in response to receipt of the packet of first arrival for requesting a search for a mobile station specified by the packet of first arrival. The gateway then transmits the packet of first arrival to one of the routers which responds with a reply message, and transmits the packet of second arrival to the responding router if the packet of second arrival is received before a predetermined time interval expires, and transmit a disconnect signal to the responding router if the predetermined time interval expires after the transmission of each of the packets of first and second arrival. Each of the routers is arranged to respond to the request message with the reply message if the specified mobile station is found in the memory to receive the packets of first and second arrival and establish a connection to the specified mobile station via the corresponding wireless access network, transmit the received packets to the specified mobile station over the established connection, and clear the connection in response to the disconnect signal.
According to a second aspect, the present invention provides a method of communication for a system comprising a gateway connected to a connectionless data network, a plurality of routers connected to the gateway, and a plurality of wireless access networks, connected respectively to the routers, for establishing wireless links with mobile stations, each of the routers including a memory for storing location data of mobile stations. The method comprises the steps of (a) receiving a packet of first arrival from the connectionless data network at the gateway, (b) transmitting a request message from the gateway to all of the routers in response to receipt of the packet for requesting a search for a mobile station specified by the packet of first arrival, (c) making a search through the memory of each of the routers in response to the request message from the gateway, (d) receiving, at one of the routers, the packet from the gateway if the specified mobile station is found in the memory of the one router, and (e) routing the received packet via the corresponding wireless access network to the mobile station.
According to a third aspect of the present invention, the method of communication comprises the steps of (a) receiving, at the gateway, packets of first and second arrival of same destination from the connectionless data network, (b) transmitting a request message from the gateway to all of the routers in response to receipt of the packet of first arrival for requesting a search for a mobile station specified by the packet of first arrival, (c) making a search through the memory of each of the routers in response to the request message from the gateway, (d) transmitting a reply message from one of the routers to the gateway if the specified mobile station is found in the memory of the router, (e) transmitting the packets from the gateway to the router in response to the reply message; and (f) receiving, at the router, the packets from the gateway and routing the received packets via the corresponding wireless access network to the mobile station.
According to a fourth aspect of the present invention, the method of communication comprises the steps of (a) receiving, at the gateway, packets of first and second arrival of same destination from the connectionless data network, (b) transmitting a request message from the gateway to all of the routers in response to receipt of the packet of first arrival for requesting a search for a mobile station specified by the packet, (c) making a search, at each of the routers, through the memory of the router in response to the request message and transmitting a reply message back to the gateway from one of the routers if the specified mobile station is found in the memory of the router and establishing a connection from the router to the specified mobile station via the corresponding wireless access network, (d) transmitting, from the gateway to the router, the packet of first arrival in response to the reply message, (e) transmitting, from the gateway to the router, the packet of second arrival if the packet of second arrival is received before a predetermined time interval expires, (f) transmitting, from the gateway to the router, a disconnect signal if the predetermined time interval expires after the transmission of each of the packets of first and second arrival, (g) transmitting the packets of first and second arrival from the router to the specified mobile station over the established connection, and (h) clearing the connection in response to the disconnect signal.